Notifications for JIRA adds another Then-action possibility in your Servicedesk automation rules.
To send an SMS when issues require your attention, go to your project's automation settings, and add a new automation rule or update an existing one.
Select 'Send SMS' from the drop-down of Then actions.
Fill in the message you want to send (see replacement variables to add issue-based information), and select the destination to whom you want to send the text message. You can choose between: a user defined in the issue (assignee, reporter, custom fields) each user in a group defined in the issue (custom fields) a fixed user each user from a fixed group * a fixed phone number 
Press confirm, and save your automation rule, and you're good to go!